How long until we see a true multitasking OS?

[Smilin]

Originally posted by: Brazen

Originally posted by: Smilin


The BSOD is still there.

The black notes screen is the screen where everything goes black and flips into text mode with ascii music notes displayed while a tone sounds. It's the graphics driver being loaded and the graphics card being initialized. Pulling this off outside of the boot process is pretty impressive.

How is that impressive? Unix systems could do that since Xwindows existed.

How are you going to drop to the command line and see anything while your video card is rebooting?

We're not talking about restarting the shell here (kill explorer.exe and restart), we're talking about shutting down the video card and restarting it.

 

[Nothinman]

We're not talking about restarting the shell here (kill explorer.exe and restart), we're talking about shutting down the video card and restarting it.

Yea, we do that too. When you switch to a VT in Linux you're using the VGA (or possibly framebuffer) driver and when you switch back to X you're using the driver that X was configured for. Obviously that isn't a complete video POST since that isn't necessary and would take too long for a simple VT->X switch, but X can POST cards if necessary because a lot of time secondary cards don't get POSTed by the BIOS and need to be before X can use them.

 

[Smilin]

Originally posted by: Brazen

Originally posted by: drag
Well normally with X you'd have to ssh into the machine and stop restart it that way. There is no automatic detection and reset if the GUI goes south.

Well, yes, it is not automatically detected, so I would say that is somewhat impressive on Windows, but it can be done outside the boot process.

Also, I was pretty sure there was a hotkey to kill X and drop you back into a terminal if the "GUI goes south."

How are you going to have a terminal if your graphics card is rebooting?

 

[xtknight]

Originally posted by: Smilin

Originally posted by: Brazen

Originally posted by: drag
Well normally with X you'd have to ssh into the machine and stop restart it that way. There is no automatic detection and reset if the GUI goes south.

Well, yes, it is not automatically detected, so I would say that is somewhat impressive on Windows, but it can be done outside the boot process.

Also, I was pretty sure there was a hotkey to kill X and drop you back into a terminal if the "GUI goes south."

How are you going to have a terminal if your graphics card is rebooting?

SSH.

 

[spyordie007]

Originally posted by: xtknight

Originally posted by: Smilin

Originally posted by: Brazen

Originally posted by: drag
Well normally with X you'd have to ssh into the machine and stop restart it that way. There is no automatic detection and reset if the GUI goes south.

Well, yes, it is not automatically detected, so I would say that is somewhat impressive on Windows, but it can be done outside the boot process.

Also, I was pretty sure there was a hotkey to kill X and drop you back into a terminal if the "GUI goes south."

How are you going to have a terminal if your graphics card is rebooting?

SSH.

Read that string of quotes again...

 

[compressor]

The Commodore Amiga O/S was a true multi-tasking environment and it
was in the early 1990s.
It was also the first multimedia machine. I owned several and
was sad when they went under to to corrupt management.

The OS, however, does still live (somewhere)

 

[drag]

Originally posted by: spyordie007

Originally posted by: xtknight

Originally posted by: Smilin

Originally posted by: Brazen

Originally posted by: drag
Well normally with X you'd have to ssh into the machine and stop restart it that way. There is no automatic detection and reset if the GUI goes south.

Well, yes, it is not automatically detected, so I would say that is somewhat impressive on Windows, but it can be done outside the boot process.

Also, I was pretty sure there was a hotkey to kill X and drop you back into a terminal if the "GUI goes south."

How are you going to have a terminal if your graphics card is rebooting?

SSH.

Read that string of quotes again...

Yep. Most people don't have a second computer sitting around just in case the video drivers they are using are ******.

In Linux there are a few manual things you can do if X hanges...

ctrl-alt-F1 to switch to console. The console drivers are different from teh X drivers and there may be some resetting going on that will help you escape from a hung X session. Sometimes it will switch and you can type out stuff, but the screen will still be blank. In that case you can hit ctrl-alt-del to reboot.

if that doesn't work...

ctl-alt-backspace will cause you to kill X very aggressively. This will help you to break out of it.

if that doesn't work...

Then you can use the magic sysrq key combo to sync you disks and trigger a reboot. The magic sysrq key causes the kernel to listen for a certain key combination directly from the keyboard causing it to bypass any stuff that may be borked in userspace.

Basicly you hit alt-sysrq-s key (usually also the printscr) to 'sync' disks, then alt-sysrq-b to reboot. The downside to ths is that sysrq key is disabled by default since it's a huge security risk, but it is very simple to enable if you are having problems.

http://en.wikibooks.org/wiki/Linux_Guide/Freezes

 

[Nothinman]

The downside to ths is that sysrq key is disabled by default since it's a huge security risk, but it is very simple to enable if you are having problems.

It's enabled by default in Debian (and as such probably Ubuntu) and Fedora.

 

[spyordie007]

How is enabling sysrq a "huge security risk"? You have to have physical access to the machine to make the keystroke...

 

[Nothinman]

How is enabling sysrq a "huge security risk"? You have to have physical access to the machine to make the keystroke...

Actually there's also a /proc counterpart to it, "echo -n s > /proc/sysrq-trigger" will work as if you hit alt+sysrq-s locally. The file is writable only by root though so you would still need another exploit before you could use that.

 

[drag]

Originally posted by: spyordie007
How is enabling sysrq a "huge security risk"? You have to have physical access to the machine to make the keystroke...

Yes. And if your actually using Linux for anything other then your home desktop then that is a problem.

While physical access to machines is always problematic in terms of security... Having a magic keystroke that can allow instant access to your machine without password and completely bypasses any and all security restrictions seems like a very bad idea.

Like you use Linux as a in desktop at some business or you have administrators that are suppose to be only allowed to perform certain functions.

 

[spyordie007]

Having a magic keystroke that can allow instant access to your machine without password and completely bypasses any and all security restrictions seems like a very bad idea.

I thought it dropped you to the CLI, and you still had to log in? Is this not the case?

 

[Nothinman]

The sysrq keystroke doesn't even do that, it'll just let you do some debugging stuff and hard reboot the system. And the latter can be done with the power cord or button if you really wanted.

 

[drag]

Ya, it just sends commands.
Sort of like just going ctl-alt-del in the console, of course a bit lower-level though. There isn't a whole whole lot you can do with it.

One part that may have some mischeif potential is kexec. On a machine configured to use this stuff with alt-sysrq-c you can trigger a kernel panic and then load up a alternate kernel image to debug the kernel without having to go through a entire reboot procedure.

Kexec is a rather new feature for Linux that allows you to boot into alternate kernels without going through a full reboot. You avoid the bios and all that mess. You would use it in environments were aviability is important and if your adeveloper trying out different things like utilizing some of the debugging features that can be used.